GEOLOGY

Detailed explanation-1: -Molds form when shells or bones dissolve, leaving behind an empty depression; a cast is then formed when the depression is filled by sediment. Replacement occurs when the original shell or bone dissolves away and is replaced by a different mineral; when this occurs with permineralization, it is called petrification .

Detailed explanation-2: -Fossils form in five ways: preservation of original remains, permineralization, molds and casts, replacement, and compression. Rock formations with exceptional fossils are called very important for scientists to study. They allow us to see information about organisms that we may not otherwise ever know.

Detailed explanation-3: -We find molds where an animal or plant was buried in mud or soft soil and decayed away, leaving behind an impression of their bodies, leaves, or flowers. Casts are formed when these impressions are filled with other types of sediment that form rocks, which take the place of the animal or plant.

Detailed explanation-4: -Scientists categorize fossils into three main groups-impression fossils, trace fossils, and replacement fossils. Amber is also often looked at as the fourth type of fossil but, even though a chunk of amber can contain insects that were trapped in resin long ago, technically it is still categorized as a gemstone.

Detailed explanation-5: -Fossil molds and casts preserve a three-dimensional impression of remains buried in sediment. The mineralized impression of the organism left in the sediment is called a mold. The mineralized sediment that fills the mold recreates the shape of the remains. This is called a cast.